What is meant by moral relativism in this case I think is merely that morals do not come to us handed down by God or Nature as Chomsky claims, but are a constant choice made by people over a potentially infinite range. But to assert that the morals don't come from God is not to say that morals are not valuable or worth having.
As Foucault puts it, "What is good, is something that comes through innovation. The good does not exist, like that, in an atemporal sky, with people who would be like the Astrologers of the Good, whose job is to determine what is the favorable nature of the stars. The good is defined by us, it is practiced, it is invented. And this is a collective work."
1. http://www.critical-theory.com/read-me-foucault-interview-in...